R dataframe：将多行上的值转换为列表

Question

I want to transform this:

library(tibble)
(
  tribble(
    ~id, ~value,
## -----|--------| 
     1,   "qwer",
     1,   "asdf",
     2,   "uiop",
     3,   "zxcv",
     3,   "qwer",
     3,   "uiop" )
) -> input

into this:

(
  tribble(
    ~id,          ~values,
## -----|------------------------------| 
     1,   list("qwer", "asdf"),
     2,   list("uiop"),
     3,   list("zxcv", "qwer", "uiop"))
) -> output

Please note that the number of disinct values is not known...

Answer 1

Edit in view of comment below

If you want to store each value as list containing every value as distinct item, please do it like this

input %>% group_by(dummy = row_number()) %>%
  mutate(value = list(value)) %>%
  ungroup() %>% group_by(id) %>%
  summarise(value = list(value))

# A tibble: 3 x 2
     id value     
  <dbl> <list>    
1     1 <list [2]>
2     2 <list [1]>
3     3 <list [3]>

#check its structure
output <- input %>% group_by(dummy = row_number()) %>%
  mutate(value = list(value)) %>%
  ungroup() %>% group_by(id) %>%
  summarise(value = list(value))

output$value[[1]]
[[1]]
[1] "qwer"

[[2]]
[1] "asdf"

#OR
output$value
[[1]]
[[1]][[1]]
[1] "qwer"

[[1]][[2]]
[1] "asdf"


[[2]]
[[2]][[1]]
[1] "uiop"


[[3]]
[[3]][[1]]
[1] "zxcv"

[[3]][[2]]
[1] "qwer"

[[3]][[3]]
[1] "uiop"

old answer this will store item in a vector first and then in a list (single item)

Use this

input %>% group_by(id) %>% summarise(value = list(value))

# A tibble: 3 x 2
     id value    
  <dbl> <list>   
1     1 <chr [2]>
2     2 <chr [1]>
3     3 <chr [3]>

#check its items

output <- input %>% group_by(id) %>% summarise(value = list(value))

output$value[[1]]
[1] "qwer" "asdf"

#OR
output$value
[[1]]
[1] "qwer" "asdf"

[[2]]
[1] "uiop"

[[3]]
[1] "zxcv" "qwer" "uiop"

sample data output is as under (which matches first syntax) still second one is suggested unless any specific reason to do so.

output$value
(
  tribble(
    ~id,          ~values,
    ## -----|------------------------------| 
    1,   list("qwer", "asdf"),
    2,   list("uiop"),
    3,   list("zxcv", "qwer", "uiop"))
) -> output

output$values

[[1]]
[[1]][[1]]
[1] "qwer"

[[1]][[2]]
[1] "asdf"


[[2]]
[[2]][[1]]
[1] "uiop"


[[3]]
[[3]][[1]]
[1] "zxcv"

[[3]][[2]]
[1] "qwer"

[[3]][[3]]
[1] "uiop"